The invention relates to a multi-stage pump rotor of a turbomolecular pump.
Turbomolecular pumps according to the state of the art are operated at rotational speeds of several 10,000 r/min. In relatively large turbomolecular pumps, the kinetic energy of a pump rotor operated at such a nominal rotational speed is in the range of the kinetic energy of a compact car at a velocity of 50 to 70 km/h. In case of a rotor burst, this high kinetic energy will cause a massive potential of destruction and injury which can be kept under control only by considerable expenditure for the mechanical shielding of the rotor.
Particularly cantilevered pump rotors for turbomolecular pumps that are magnetically supported, will be problematic with regard to their susceptibility to bursting. In magnetically supported pump rotors of the cantilevered type, designers will aim to arrange at least one radial bearing and the drive motor in the region of the center of gravity of the pump rotor. For this purpose, it is required that the pump rotor is of a bell-shaped configuration so that the magnetic bearing and optionally also the drive motor CaO be accommodated in the bell cavity within the pump rotor. Said bell-shaped configuration of the pump rotor will entail a design-inherent weakening of the rotor. In pump rotors of turbomolecular pumps, being normally formed as a one-part unit, this design-inherent weakening can be compensated for only by use of highly resistant aluminum alloys which are extremely expensive.